I have a '71 340 that had the 90° adapter oil filter on it. I am swapping it for a standard base so the filter screws right onto the side of the block.
The only one I have is off of a '69 318...see pic.

Is there anything wrong w/ drilling the extra 4 holes in this one like the 340/360 plates have? Instead of buying another one.

I had a old plate that I put 8 holes in..
worked out great.. the other plates that
I had already had 8 holes

X2 I've done it several times as well. Just be careful that the drill doesn't wander too close to the sealing surface, and chamfer the holes when done.

Me too

Nice, thanks yall!

If your using the old oem side mount filter you can also drill 2 or 4 small holes in the bolt as the oem has only 2 small slots, the newer mp bolt uses holes in a nice pattern for alot of flow.

EV2...no, I'm getting rid of the 90° adapter.

Da, thats right, not sure what I was thinking, I dont like the 90-s myself.

All I've heard is how the 90° adapters are leak prone and I don't need one anyway w/ the factory '71 manifolds.

ok maybe this one.... the eight holes like many posted about and it looks like you have the open round center fastener vs the restrictive square one.

One time I drilled the center a bit bigger but not really sure if it helped because there are so many other restrictive places.

Yes, that's what I'm looking to make. I don't have much small block stuff and the only adapter plate I have here is off a 318...which only has 4 holes.

I have done the same as well, I even drilled the square hole out of the middle of the hold down. I used one of the fancy Canton plates on the current motor though.

Maybe I'm thinking wrong but compare the combined surface area of the four holes in the plate to the surface area of the hole in the block. The block is the restriction.

The abrupt size change of the filter holes is a "vena contracta", or restriction far worse than the actual size suggests. By comparison, a long shallow taper leading to and from the same size hole flows much better - but no way to do that.
I blend and radius every oil passage I can reach.

Isn't that called a "Venturi" Which enhances flow, correct

a tapered reamer would work for that. many sizes available. not outrageous prices, depending on size needed.

Same here............